FRM-16606

FRM-16606 is a selective small-molecule inhibitor of phosphodiesterase 9 (PDE9), an enzyme that specifically degrades cyclic guanosine monophosphate (cGMP). By inhibiting PDE9, the drug increases intracellular cGMP levels, which are crucial for dopamine signaling pathways in striatal projection neurons. Developed by Forum Pharmaceuticals, FRM-16606 has been investigated for its potential to enhance the therapeutic effects of l-DOPA in Parkinson's disease. Research in non-human primate models indicates that FRM-16606 can significantly prolong the "on" state of l-DOPA without exacerbating dyskinesias or altering l-DOPA pharmacokinetics, suggesting that striatal PDE9 inhibition may be a viable strategy to improve motor responses in patients with advanced parkinsonism.